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Relationships among the 18 extant species of parasitic lamprey (Petromyzontiformes) were determined using a cladistic analysis of 32 mainly morphological characters. Because previous analyses support all known fossils as phylogenetically older or the same age as living lampreys, a composite agnathan fossil was used as an outgroup. A consensus of three equally parsimonious trees revealed a trichotomy between a monophyletic northern hemisphere clade and the southern hemisphere genera Geotria and Mordacia. The monophyletic status of the northern hemisphere lampreys and their classification in a single family Petromyzontidae was corroborated. It is suggested that the two southern hemisphere lamprey genera be retained as distinct families. Among northern hemisphere species, Ichthyomyzon and Petromyzon form a monophyletic group sister to the remaining genera. Caspiomyzon is sister to TetrapleurodonEntosphenusLethenteronEudontomyzonLampetra, with Tetrapleurodon in turn being sister to a group comprising Entosphenus and a clade containing Lethenteron and its sister group EudontomyzonLampetra. Differences in many characters are related to differences in modes of feeding and behavior. In a phylogenetic context, dentitional characters are resolved as related either to blood feeding (Petromyzon, Ichthyomyzon, and Mordacia) and hypothesized to be plesiomorphic, or to flesh feeding (Eudontomyzon, Lampetra, and Geotria).
Current theory predicts that (1) locomotor performance of amphibians should exhibit greater thermal sensitivity in aquatic than in terrestrial habitats, and (2) amphibians lose the ability to acclimate locomotor performance to different temperatures after metamorphosis. To test these predictions for a semiaquatic plethodontid salamander (Pseudotriton ruber), I measured aquatic and terrestrial burst speeds of metamorphosed individuals at 8 C and 18 C after acclimation to 8 C and 18 C. Both aquatic and terrestrial speeds exhibited thermal sensitivity, which paralleled that for cycle frequency (tail or leg), but terrestrial speed had a significantly greater thermal sensitivity. Aquatic speed was significantly greater at 8 C acclimation, whereas terrestrial speed was not affected by thermal acclimation. Scaling of locomotor performance was significantly different in water than on land and was significantly affected by temperature. My results indicate that (1) aquatic burst speed has less thermal sensitivity (perhaps related to a greater importance of burst speed in aquatic habitats), and (2) a partial positive compensation in aquatic burst speed occurs at low acclimation temperature (perhaps related to seasonal activity in cool aquatic habitats). However, because the compensatory increase in swimming speed at low acclimation temperature was much less at low test temperature (a 6% increase) than at high test temperature (an 18% increase), this may not be a beneficial acclimation response.
A phylogenetic analysis of Danio (sensu lato), based on 38 morphological characters, shows that Danio, as recognized until now, is paraphyletic. Danio is restricted to species previously recognized as the “Danio dangila species group,” including D. dangila, Danio rerio, Danio nigrofasciatus, and Danio albolineatus. Those species share an “A stripe” on the anal-fin rays, an anterior lateral extension ventrally on the dentary, two or more pigment stripes on the caudal-fin rays and greatly enlarged lamellar nasal. Esomus is the sister group of Danio. Remaining Danio (sensu lato) species are referred to Devario, characterized by a short and wide premaxillary ascending process with a minute apophysis contacting the kinethmoid, a short maxillary barbel, a “P stripe” extending onto the median caudal-fin rays, and infraorbital 5 not or only slightly reduced. Devario includes the species Devario malabaricus, Devario kakhienensis, Devario devario, Devario chrysotaeniatus, Devario maetaengensis, Devario interruptus, and Devario apogon. The sister group of Devario is a clade composed of Inlecypris and Chela. The well-known genus Brachydanio becomes a junior synonym of Danio (sensu stricto). The phylogenetic relationships of small Danio-like species Sundadanio axelrodi, Danionella translucida, Danio erythromicron, and Microrasbora rubescens remain unresolved.
We studied the reproductive and nesting ecology of the Yellow-Blotched Map Turtle (Graptemys flavimaculata) from 1993–1994 and from 1996–1997 on the Pascagoula River in southeastern Mississippi. This species has undergone a recent decline leading to its listing as Threatened under the U.S. Endangered Species Act. We found three distinctive features of the biology of this population: a relatively low reproductive frequency compared with most other map turtles (maximum of 1.16 clutches/female), a very high level of nest mortality caused by river flooding and fish crow predation (90% mortality in some years), and an unexpectedly high level of nesting in shaded areas along the riverbank, perhaps in response to human disturbance on and near sandbars. Our data suggest that, in the absence of extraordinarily high adult survival, this population will decline because of low recruitment. We suggest a series of specific strategies to reverse these declines, including better law enforcement to protect adult turtles, public education, and possibly, protection of nests on the nesting beaches.
Based on examination of 655 ciscoes from Lake Saganaga, a Minnesota/Ontario border lake, three forms, about 90% separable on gill raker counts, are present. Form L, with the lowest gill raker counts (26–40, mean = 31.9, n = 96) is tentatively identified as Coregonus zenithicus. Form M, with intermediate gill raker counts (36–50, mean = 43.1, n = 92) was the only cisco anticipated to occur in lakes of the region and is assumed to represent Coregonus artedi. Form H, with 45–70 gill rakers, mean = 56.1, n = 467, is the most common cisco in the lake. We argue that the appropriate name for this form is Coregonus nipigon. Additional differences among the three forms include lateral-line scale and vertebral counts, gill raker length, body shape, fin pigmentation, size at sexual maturity, and maximum size. Seagull Lake, affluent to Lake Saganaga, contained only C. artedi (n = 108). Gunflint and Magnetic Lakes, also affluents to Lake Saganaga, contained C. artedi (n = 19) and C. zenithicus (n = 29). Lake Saganagons, immediately downstream of Lake Saganaga, based on only eight available specimens, appears to contain C. nipigon (7) and C. artedi (1).
Many evolutionary processes have been identified that could lead to signal variability among populations despite stabilizing selection to maintain conspecific recognition. By examining among-population variation in mate recognition signals we may gain insights into the processes behind the evolution of such variation. We documented among-population variation in the advertisement call of Litoria verreauxii in the Australian Snowy Mountains to determine how call structure varied (1) across a broad geographic area, (2) from allopatry to sympatry with northern Litoria ewingii (an undescribed member of the same species complex), and (3) between two subspecies, Litoria verreauxii verreauxii and Litoria verreauxii alpina. Significant variation in all measured call properties was explained by latitude and/or longitude. Most noticeably, a strong east-west trend in introductory note duration and pulse number was detected that coincided with the transition from allopatry to sympatry with northern L. ewingii. The observed variation is discussed within the context of several evolutionary mechanisms including clinal variation and both reproductive and ecological character displacement. We found considerable variation in pulse rate among nearby allopatric populations (based upon current taxonomy). Pulse rate has been implicated in species recognition and reinforcement in L. verreauxii. Some of the among-population variation in pulse rate may reflect the presence of cryptic taxa. However, these results suggest that factors other than interspecific interactions with closely related species can lead to considerable among-population divergence in pulse rate. Finally, there was little difference in call structure between the two subspecies.
We studied growth, condition, spawning period, activity patterns, and movement in the Salish Suckers of Pepin Brook in British Columbia's Fraser Valley. Radio-telemetry showed that fish were crepuscular, had home ranges averaging 170 m of linear channel, made their longest movements during the spawning period (March to early July), and rarely crossed beaver dams. Relative to closely related catostomids, Salish Suckers are small, early maturing, and have a prolonged spawning period. These characteristics are likely to impart good resilience to short-term disturbances of limited spatial scale and to facilitate successful reintroductions to suitable habitat. The chronic, large-scale disruptions that affect their habitat in Canada, however, are likely to cause further extirpations over time. Given its limited geographic distribution, management of the Salish Sucker should focus on protecting all remaining habitat and exploiting opportunities for habitat restoration and reintroduction into suitable habitats throughout their historic range.
Ontogenetic shifts in diet are common for snakes, and such shifts in diet for venomous snakes may be associated with changes in venom composition. The present study investigated whether an ontogenetic shift in diet and venom composition, as observed for Crotalus oreganus helleri and Crotalus oreganus oreganus, occurs in Crotalus oreganus concolor. Like C. o. helleriandC. o. oreganus, and at similar body sizes, C. o. concolor show an ontogenetic shift in diet. Juvenile snakes primarily feed on small lizards, whereas adults typically consume small rodents. However, C. o. concolor do not show the same pattern of venom ontogeny as do C. o. helleri and C. o. oreganus.
Because of the presence of a phospholipase A2-based β-neurotoxin (concolor toxin) and several myotoxins, C. o. concolor venom is particularly toxic, but mouse LD50 assays demonstrated no significant difference in toxicity between adult (0.38 μg/g) and juvenile (0.45 μg/g) venoms. Metalloprotease activity (correlated with extensive tissue damage and prey predigestion) was extremely low in both juvenile and adult venoms. Levels of peptide myotoxins and several serine proteases that interfere with hemostasis (specifically thrombin-like and plasmin-like activities) showed a positive correlation with size. Human envenomations recorded during this study showed symptoms consistent with biochemical analyses, with numbness associated with the bite, coagulation abnormalities and essentially no tissue damage. Results suggest that the occurrence of potent neurotoxic component(s) in a venom minimizes predigestive components (metalloproteases). Further, concurrence of these functional components in the venom of an individual may be selected against, and highly toxic venom in both juvenile and adult C. o. concolor may represent a form of venom paedomorphosis.
Gambusia clarkhubbsi (San Felipe Gambusia) is described from San Felipe Creek, a spring-fed Rio Grande tributary in Del Rio, Texas. The new species is distinguished from other members of the Gambusia nobilis species group by a combination of morphometric and pigmentation characters. It appears to prefer thermally consistent spring flows and is apparently most common in edge habitats adjacent to flowing waters.
We describe a new microhylid frog from the rain forests of central eastern Madagascar. Plethodontohyla coronata reaches 21–23 mm snout–vent length and is similar to Plethodontohyla serratopalpebrosa by having a supraocular crest of three dermal spines. It differs by having a smaller body size, shorter hind limbs, relative finger and toe length, and smaller relative tympanum size. Its first toe is very short, reminiscent of the state in miniaturized species of Stumpffia, but the presence of vomerine and maxillary teeth clearly confirm the assignation of P. coronata to Plethodontohyla. The advertisement call of this fossorial frog is a series of notes with complex frequency modulation.
‘Cichlasoma’ scitulum, new species, is described from the Río Rosario drainage in the Río de La Plata region of Uruguay, and from lower Río Uruguay tributaries in Argentina, Uruguay and Brazil. It is easily distinguished from the other two species of the ‘Cichlasoma’ facetum group in meristic and coloration characters. ‘Cichlasoma’ scitulum has the highest anal-fin spine counts of the three species and it is also characterized by having black-spotted dorsal, anal and caudal fins and flank and opercular scales.
Steatogenys ocellatus é descrita como uma espécie nova proveniente de localidades próximas às cidades de Tefé (Brasil) e Iquitos (Perú) na Bacía Amazônica. Esta espécie é descrita com base em características de morfologia externa, dados merísticos, pigmentação, osteologia e propriedades das descargas do órgão elétrico (DOE). Steatogenys ocellatus diferencia-se das duas outras espécies do gênero, S. elegans e S. duidae, pelas seguintes características: (1), tamanho máximo do corpo relativamente grande (comprimento máximo até o limite posterior da nadadeira anal 320 mm vs. 172 mm nas outras espécies); (2), uma mancha nítida com forma redonda ou oval na base da nadadeira peitoral; (3), nadadeira peitoral com manchas escuras e irregularmente distribuídas. Steatogenys ocellatus também diferencia-se inequívocamente das outras espécies do gênero por várias características morfométricas e merísticas. Steatogenys elegans é comum em habitats lacustres e fluviais e é amplamente distribuida nas bacías dos rios Amazonas e Orinoco, e nas Guianas. Steatogenys duidae occore em igarapés de terra firme e é também amplamente distribuida nas bacías do Rio Amazonas e Rio Orinoco (mas ausente nas Guianas). O habitat de S. ocellatus constitui-se de sistemas de águas pretas com condutividade baixa e sem correnteza (ou com correnteza muito fraca), tal como florestas sazonalmente alagáveis. Na região de Tefé, S. ocellatus occore em simpatria com S. elegans e S. duidae, contudo em sintopia exclusivamente com S. elegans.
A new species of stichaeid fish referable to the genus Lumpenopsis Soldatov is described based on two specimens from Southern California. The Saddled Prickleback, Lumpenopsis clitella n. sp., is remarkably similar in body form and coloration to the type species of the genus, Lumpenopsis pavlenkoiSoldatov, 1916, known from the northwestern Pacific. The two species differ in number of anal-fin spines (one in L. clitella vs two in L. pavlenkoi), cheek squamation (absent vs present), and in modest details of meristics and coloration. Among North American pricklebacks, the Saddled Prickleback is most similar to the Y-Prickleback, Allolumpenus hypochromusHubbs and Schultz, 1932. The holotype and only specimen on which the descriptions of that genus and species were based, reportedly lacked vomerine and palatine teeth, a character used to distinguish Allolumpenus from Lumpenopsis. The holotype of A. hypochromus cannot be located, but examination of two more recently collected specimens indicates the presence of both vomerine and palatine teeth in the Y-Prickleback. Consequently, Allolumpenus Hubbs and Schultz is considered a junior synonym of Lumpenopsis Soldatov. We provide a diagnosis of Lumpenopsis and key to the four included species: L. pavlenkoi Soldatov and Lumpenopsis triocellata (Matsubara) from the northwestern Pacific, and Lumpenopsis hypochromis (Hubbs and Schultz) and L. clitella n. sp. from the northeastern Pacific. Lumpenopsis exhibits a North Pacific distribution similar to that of other stichaeids.
Symphurus bathyspilus, which attains standard lengths up to 121 mm, is described on the basis of 84 specimens collected in deep waters (248–500 m) in the Philippine Archipelago and off Indonesia. This species is characterized by the combination of a predominant 1–2–2 pattern of interdigitation of dorsal pterygiophores and neural spines; 14 caudal-fin rays; 91–100 dorsal-fin rays; 78–87 anal-fin rays; 50–54 total vertebrae; five hypurals; black peritoneum; uniformly bright reddish-brown (freshly captured) to darker reddish-brown ocular side sometimes with faint incomplete cross-bands; uniformly yellowish to straw-colored blind side with numerous small reddish-brown speckles overlying regions of proximal pterygiophores of the blind sides of the dorsal and anal fins; with dorsal and anal fins darker reddish-brown anteriorly, gradually fading to a pale reddish color in their posterior regions; and with the outer surface of the ocular-side opercle yellowish with reddish-brown speckles. Among congeners, the new species is most similar in some meristic features to those of Symphurus woodmasoni but differs markedly in its ocular- and blind-side coloration, in the pigmentation of its dorsal, anal, pelvic, and caudal fins and its yellowish and speckled ocular-side outer opercular surface.
Liparis adiastolus, a previously undescribed species from the coasts of Oregon and Washington, northwest United States, is described. The new species has probably been consistently confused with Liparis rutteri, which has a more northerly distribution. Liparis adiastolus is clearly distinguishable from all similar species in having 41–70 pyloric caeca, 35–39 vertebrae, 30–33 dorsal-fin rays, 32–35 pectoral-fin rays, disk 67–77% HL, and other distinctive characters. In addition to describing the new species, we select a lectotype of L. rutteri, provide an expanded diagnosis for that species, and discuss the confusion previously existing with regard to its identification.
A second species of Cyphotilapia (Cichlidae) is described from Lake Tanganyika. The new species is clearly distinct from Cyphotilapia frontosa in having three scale rows between the upper and lower lateral lines at center of body (vs two rows in C. frontosa). Furthermore, a greater number of scales on the longitudinal line (34–36 vs 33–35), fewer outer teeth on the upper jaw (31–52 vs 39–62), higher body (43.3–51.2% SL vs 38.2–46.5%), longer predorsal (37.5–44.9% SL vs 37.1–42.7% SL), longer dorsal-fin base (57.1–64.6% SL vs 53.8–60.9% SL) and longer pectoral fin (36.0–47.2% SL vs 31.3–41.7%) also distinguish the former species. The distribution of the new species is restricted to the southern half of Lake Tanganyika, whereas C. frontosa is allopatrically distributed in the northern half of the lake.
The location of the holotype of Rhombus cocosensis Bleeker (presently known as Engyprosopon cocosensis) has been listed as unknown. The alleged holotype was found recently in Leiden (RMNH) and examined confirming it as the holotype. It has palmate gill rakers, a type of gill raker limited, within the Bothidae, to the genus Asterorhombus. Thus, Asterorhombus cocosensis is a nominal species of that genus. “Engyprosopon cocosensis” of has no palmate gill rakers and was an obvious misidentification made without examing the holotype. There is no junior synonym for this fish. The purpose of this paper is to name the species and redescribe it.
The claustrum, one of the Weberian ossicles of otophysans, is here proposed as homologous to the accessory neural arch (ANA) of lower teleosts. This idea is based on structural and topographical correspondence, as well as on ontogenetic timing of differentiation and ossification. Claustrum and ANA are similar in general shape and occupy the same position relative to other vertebral structures. They are both derived from paired cartilage precursors that differentiate around the anterior part of the neural canal. Also, chondrification and ossification of ANA and claustrum are markedly delayed relative to surrounding elements, such as regular neural arches and supraneurals. The new hypothesis implies that the accessory neural arch is actually present in otophysans (modified as claustrum) and therefore that its loss cannot be considered as an ostariophysan synapomorphy. Loss of a separate accessory neural arch in adults is instead an additional synapomorphy of Gonorynchiformes, a loss homoplastic with various other teleostean subgroups, the largest of which being Ctenosquamata. Despite various developmental differences, ANA may be a basidorsal derivative and therefore homologous to the neural arch series.
Gopher Tortoises (Gopherus polyphemus) are thought to exhibit harem defense polygyny because adult females that are relatively aggregated are thought to receive increased rates of mating visits by large, dominant males relative to females that are more isolated. To examine this expected pattern, we regressed rates of social behaviors on (1) degree of isolation of burrows occupied by female tortoises and (2) degree of isolation of female tortoises. The rate at which other tortoises visited a female was negatively associated with degree of isolation of burrows and females. However, we found no relationship between rates of behaviors associated with reproduction (interactions, courts, and mounts) and degree of isolation of burrows or females. Additionally, there was no association between degree of isolation of females and the number or body mass of males that mounted them. These results indicate that, for large, contiguous populations of Gopher Tortoises in high-quality habitat, such as our study site, distance from neighboring tortoises does not affect mating opportunities of reproductive females. Our findings suggest that patterns of reproduction of Gopher Tortoises conform more closely to expectations of scramble-competition polygyny than to harem defense polygyny.
We examined oral grasping behavior, a unique and relatively unknown method of maintaining station against flow, in nine species of North American cyprinids to determine whether oral grasping was used by a range of cyprinid species and to further investigate the relationship between oral grasping and water velocity. Fish were subjected to a stepwise increasing velocity test in a 100-liter laboratory swim tunnel that had wire mesh (0.6-mm diameter) attached to a flow filter serving as the grasping substrate. Frequency and duration of oral grasping events were noted for a particular fish during each velocity increment. We observed 608 grasping events, and oral grasping behavior was exhibited by all nine species examined. Mean number of grasping events was high (28.4/trial) for Cyprinella venusta, intermediate (approximately 18/trial) for Cyprinella camura, and Notropis longirostris, and low (< 5/trial) for Notropis texanus, Notropis maculatus, and Notropis wickliffi. Although critical swimming speed varied among species, the water velocity at which oral grasping behavior initially appeared (threshold grasping velocity), expressed as a percentage of critical swimming speed, was approximately 70–80% for most species tested. Oral grasping may be triggered by the onset of muscular fatigue, and is an attempt by minnows to maintain position in water velocities exceeding aerobic swimming ability. We speculate that minnows in lotic environments use oral grasping when high, energetically demanding water velocities are unavoidable, such as during a flood.
Phrynosomatid lizards show considerable variation among species in the occurrence of a secondary sexual trait, blue abdominal coloration. The production of blue skin may be controlled by at least two cellular components, melanin in melanophores, and guanine in iridophores. To examine the hypothesis that a mechanism producing variation in abdominal coloration is variation in the presence of melanin in the melanophores within the dermal layer of skin, we used light microscopy to compare melanin density of five species of phrynosomatid lizards with ancestral and derived abdominal coloration. Our results show that the skin of adults with blue abdominal coloration has more dermal melanin than white skin regardless of species or sex. We experimentally tested this relationship by examining the dermal melanin in skin from female Sceloporus undulatus consobrinus with exogenously elevated levels of testosterone or 5α-dihydrotestosterone. These females displayed malelike abdominal coloration and malelike melanin density. Our results suggest that melanin density plays a role in the presence of blue abdominal coloration in these phrynosomatid lizards.
Growth, mortality and sexual size dimorphism of Vipera latastei were investigated in northern Portugal. Size structure ranged from 16–58 cm of snout–vent length (SVL), with peaks between 40–45 cm for males and 35–40 cm for females. Age structure ranged between 0 and 14 years, with peaks at 4 and 5 years for males and at 4–6 years for females. Longevity was 11 and 14 years for males and females, respectively. Sexual maturity was attained approximately at four years in males, and one year later in females, however, at a similar body size. Growth rates decreased with increasing SVL; males grew faster than females at all ages; and asymptotic body size was larger in males than in females. Mortality was higher in males than in females and increased after sexual maturity in both sexes. The sexual differences in mortality annulled an age-specific sexual size dimorphism in favor of males and produced a minor sexual size dimorphism in mean adult body size of V. latastei.
An attempt was made to assess longevity using growth lines on bone surfaces from five, known-age, captive-raised Varanus bengalensis specimens. These monitors ranged in size from 22–52 cm SVL and spanned hatchling to adult ontogenetic stages. Growth rings were found to be prevalent within the glenoid cavities of vertebrae from all specimens. Total counts of these lines required removal of calcified cartilage deposits beforehand. Following such preparations, one to 11 growth lines were revealed. These counts strongly correspond with the known age of the specimens. It appears these structures form annually and can be used to age this taxon late into ontogeny. The methods developed here show great promise for providing a useful means to age skeletal material from the wild; however, follow-up field studies are recommended prior to such implementation.
Despite wide variation in form and function of vertebrate feeding strategies, convergent acquisitions of functionally analogous systems are seen across taxa, often driven by the medium (air or water) in which the animal lives. As the majority of fish rely on suction for aquatic prey capture, tetrapods that exhibit this mode prove especially valuable for functional morphological analysis of vertebrate response to medium constraints. The dwarf African clawed frog, Hymenochirus boettgeri, is unique among anurans as an inertial suction feeder. High-speed video recordings indicate that kinematic variables of food capture always proceed in a rostrocaudal sequence, as is conserved among suction-feeding vertebrates. However, maximum hyoid depression differs from most vertebrates studied in that it follows (rather than precedes) mouth closure. Suction events are preceded by a body lunge toward the food item and followed by recoil of the body with lateral spreading of the forelimbs. It is proposed that the abducted forelimbs decelerate the frog's capture lunges and delayed hyoid depression acts to prolong a caudal flow of water to effectively entrain prey.
We investigated differences in metabolism and locomotor performance of male and female spotted salamanders (Ambystoma maculatum) collected during the breeding season. Male salamanders had faster voluntary crawling speeds than did both gravid and postgravid females. Burst swimming velocity was higher in males than in gravid females but not postgravid females, and there was no difference in burst crawling speeds between the sexes. Oxygen consumption during rest was greater in both gravid and nongravid females than in males, but there was no difference among the three groups in oxygen consumption during locomotion. Both male and postgravid females were able to sustain terrestrial locomotion on the treadmill longer than were gravid females. These findings suggest differences in locomotor performance and energetics between the sexes that may underlie differences in arrival times at breeding sites, frequency of participation in reproductive events, and survival.
Gregarious behavior among oviparous female animals just prior to oviposition can be explained by several mechanisms, including a benefit to offspring survival. By clustering eggs together in one area, females may dilute the probability of egg predation. We tested the hypothesis that nest density influences egg survival in the Pig-Nosed Turtle (Carettochelys insculpta) along a river in northern Australia. Beaches with multiple nests were three times more likely to experience a predation event than beaches with single nests. However, the number of nests on a beach did not influence the probability of predation of individual nests, when considering either beaches with single versus groups of nests, or when comparing beaches with single nests, small groups of nests (n = 2–5), and large groups of nests (n = 6–8). Therefore, gregarious behavior of reproductive females during the nesting period did not dilute predation risk to nests. Four other hypotheses might explain the behavior: (1) nesting areas are limited; (2) nesting in groups dilutes predation risk to nesting females; (3) nesting in groups dilutes predation risk to hatchlings; and (4) social interactions in aggregations of nesting females provide additional information on nesting beaches/sites, reducing some cost associated with independent assessments of nesting beaches/sites.
Animals should tend to adjust the magnitude and characteristics of their escape responses according to the perceived levels of predation risk to cope with risk without incurring excessive costs. We analyze in the field the factors that determine the choice of escape behavior and patterns of refuge use of Wall Lizards under two simulated levels of predation risk and under variable environmental conditions, which may affect risk perception and costs of refuge use. The results show that Wall Lizards adjusted their antipredatory response according to several factors. The threat of predation posed by the predator affected the initial type of response of lizards but not the subsequent escape strategies employed. The escape strategy depended on the vulnerability to be captured (i.e., height on the wall and air temperature) and costs of refuge use (temperature and potential predation by ambush snakes). The initial risk of predation and thermal costs of refuge use affected emergence times from the refuge. The antipredator decisions of Wall Lizards, therefore, were influenced not only by the probability of mortality in the immediate future, such as the initial threat of predation and perceived susceptibility but also by consequences for long-term expected fitness, such as physiological costs of refuge use, and by the eventual risk of mortality associated with the use of unsafe refuges.
Anolis carolinensis (Sauria: Polychrotidae) does not hibernate, and in an East Tennessee population near the northern limit of its geographic range, individuals aggregate on a south-facing rock bluff and are active throughout the winter. During the winters of 1998–1999 and 1999–2000, we obtained data on body size (snout–vent length and mass) of aggregated lizards early in the season and again in March. There was significant growth in SVL in both field seasons but in mass only in 1999–2000. Growth rate was greater in 1999–2000 than in 1998–1999, possibly attributable to the earlier onset of warmer temperatures in 1999–2000. Males grew at a greater rate than females. Our data also indicate that the winter sex ratio of aggregated individuals is male-biased.